1. Field of the Invention PA1 2. Description of the Prior Art
The present invention relates to a carbon material having a metal plated layer suitable for an electro-conductive element and a heat-conductive element and to a fabrication method thereof.
In recent years, in many industrial fields such as in home electric industries, automobile industries and aerospace industries, it has been requested to provide miniaturized, highly integrated and personalized products. Thus, electromagnetic shielding materials, light-weight electro-conductive materials, large heat-conductive materials and the like that fulfill the requirements have been developed.
Various metal materials have been used for such materials in question. However, these materials tend to be heavy.
On the other hand, since carbon materials have excellent dynamic characteristics, such as having light weight, large tensile strength, and large modulus of elasticity, as well as high electro-conductivity and large heat-conductivity, these materials have been used for structural members especially in the fields of sports industries, leisure industries, and aerospace industries. However, there have been very few applications of carbon materials based on the characteristics of their electro-conductivity and heat-conductivity, and only carbon type electro-conductive paints and bonding agents could have been found in low power electric circuits.
This is because the electro-conductivity of the carbon materials is much lower than that of metal conductors. For example, as a means for improving electro-conductivity of carbon fibers, a technology for metal-plating the surface of carbon fibers has been proposed as seen in Japanese Patent Laid-Open Publication No. 2-189811. However, in a treatment of electrolytic-plating, since the electro-conductivity of the carbon fibers is not high, a speed of film forming is slow and, moreover, a uniform film could not be formed. On the other hand, in a treatment of electroless plating, since the activation process is complicated and also a speed of film forming is slow, accordingly, the productivity has been poor.
Another type technology such as for milling or chopping continued carbon fibers of polyacrylonitrile (PAN) type or pitch type has been proposed for providing carbon fibers shortened in length. Yet further, another technology has been proposed wherein vapor-phase grown carbon fibers (VGCF) obtained through thermal decomposition of a raw organic compound by the act of catalysis of ultra fine particles of fibrous metal or metal-organic compounds, and compounding discrete carbon fibers of thus obtained VGCF with a plastic material so as to use the resultant material as a carbon fiber reinforced plastic or an electro-conductive plastic.
However, the electro-conductivity of such composite materials has an electric resistivity of 10.sup.-2 .OMEGA. cm at the most or as a limit. A metal plating treatment for such discrete carbon fibers is disclosed in, for example, Japanese Patent Publication No. 62-15637, wherein a method of pretreatment is described for forming a thin film of a noble metal on the discrete carbon fibers for electroplating. However, this method has a problem such that a uniform layer can hardly be formed on fine fibers.